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TLS and SSL

Posted by Allura on 30 08 2019.

What is Transport Layer Security (TLS)?

Transport Layer Security or TLS, is a widely adopted security protocol that provides authentication, privacy, and data integrity between two communicating computer applications. It’s the most widely-deployed security protocol used today and is used for web browsers and other applications that require data to be securely exchanged over a network, such as web browsing sessions, file transfers, VPN connections, remote desktop sessions, and voice over IP (VoIP). Many businesses use TLS to secure all communications between their Web servers and browsers regardless of whether sensitive data is being transmitted.

TLS was proposed by the Internet Engineering Task Force (IETF), an international standards organization, and the first version of the protocol was published in 1999. The most recent version is TLS 1.3, which was published in 2018

What is the difference between TLS and SSL?

TLS evolved from Netscape’s Secure Sockets Layer (SSL) protocol and has largely superseded it, although the terms SSL or SSL/TLS are still sometimes used. Key differences between SSL and TLS that make TLS a more secure and efficient protocol are message authentication, key material generation and the supported cipher suites, with TLS supporting newer and more secure algorithms. TLS and SSL are not interoperable, though TLS currently provides some backward compatibility in order to work with legacy systems. TLS version 1.0 actually began development as SSL version 3.1, but the name of the protocol was changed before publication in order to indicate that it was no longer associated with Netscape. Because of this history, the terms TLS and SSL are sometimes used interchangeably.

How does TLS work?

TLS encryption can help protect web applications from attacks such as data breaches, and DDoS attacks. Additionally, TLS-protected HTTPS is quickly becoming a standard practice for websites. For example, the Google Chrome browser is cracking down on non-HTTPS sites, and everyday Internet users are starting to become more wary of websites that don’t feature the HTTPS padlock icon.

TLS can be used on top of a transport-layer security protocol like TCP. There are three main components to TLS: Encryption, Authentication, and Integrity.

Encryption: hides the data being transferred from third parties.

Authentication: ensures that the parties exchanging information are who they claim to be.

Integrity: verifies that the data has not been forged or tampered with.

A TLS connection is initiated using a sequence known as the TLS handshake. The TLS handshake establishes a cypher suite for each communication session. The cypher suite is a set of algorithms that specifies details such as which shared encryption keys, or session keys, will be used for that particular session. TLS is able to set the matching session keys over an unencrypted channel thanks to a technology known as public key cryptography.

The handshake also handles authentication, which usually consists of the server proving its identity to the client. This is done using public keys. Public keys are encryption keys that use one-way encryption, meaning that anyone can unscramble data encrypted with the private key to ensure its authenticity, but only the original sender can encrypt data with the private key.

Once data is encrypted and authenticated, it is then signed with a message authentication code (MAC). The recipient can then verify the MAC to ensure the integrity of the data. This is kind of like the tamper-proof foil found on a bottle of aspirin; the consumer knows no one has tampered with their medicine because the foil is intact when they purchase it.

What is SSL?

SSL, or Secure Sockets Layer, is an encryption-based Internet security protocol. It was first developed by Netscape in 1995 for the purpose of ensuring privacy, authentication, and data integrity in Internet communications. SSL is the predecessor to the modern TLS encryption used today.

How does SSL/TLS work?

In order to provide a high degree of privacy, SSL encrypts data that is transmitted across the web. This means that anyone who tries to intercept this data will only see a garbled mix of characters that’s nearly impossible to decrypt.

SSL initiates an authentication process called a handshake between two communicating devices to ensure that both devices are really who they claim to be.

SSL also digitally signs data in order to provide data integrity, verifying that the data is not tampered with before reaching its intended recipient.

There have been several iterations of SSL, each more secure than the last. In 1999 SSL was updated to become TLS.

SSL certificates

SSL certificates are what enable websites to move from HTTP to HTTPS, which is more secure. An SSL certificate is a data file hosted in a website’s origin server. SSL certificates make SSL/TLS encryption possible, and they contain the website’s public key and the website’s identity, along with related information. Devices attempting to communicate with the origin server will reference this file to obtain the public key and verify the server’s identity. The private key is kept secret and secure.

The public and private keys used for SSL are essentially long strings of characters used for encrypting and decrypting data. Data encrypted with the public key can only be decrypted with the private key, and vice versa.

SSL/TSL Handshake

Every SSL/TLS connection begins with a “handshake” – the negotiation between two parties that nails down the details of how they’ll proceed. The handshake determines what cipher suite will be used to encrypt their communications, verifies the server, and establishes that a secure connection is in place before beginning the actual transfer of data. This all happens in the background, thankfully – every time you direct your browser to a secure site a complex interaction takes place to make sure that your data is safe.

The SSL or TLS handshake enables the SSL or TLS client and server to establish the secret keys with which they communicate